LOS ANGELES, March 27 (Reuters) - Incompetent teachers in California are holding back poor and minority children, an attorney for several students said on Thursday in closing arguments for a closely watched trial that could change the way public school teachers are hired and fired in the most populous U.S. state.

The lawsuit, opposed by teacher union leaders and the state, comes at a time of bitter political wrangling over how best to reinvigorate a U.S. public school system that leaves American children lagging counterparts in countries such as Finland and South Korea.

The two-month trial has focused on whether five laws meant to protect teachers' jobs are unfair to poor and minority students by putting them at a disproportionately greater risk of being taught by less effective teachers.

"We know that grossly ineffective teachers harm students," plaintiffs' attorney Ted Boutros said before a Los Angeles Superior Court judge. "When a student has a grossly ineffective teacher it harms them, it harms them for the rest of their lives."

The lawsuit touches on whether it is too difficult to fire teachers who are not effective in the classroom, and attorneys bringing the case argue the five laws they are challenging violate the civil rights of students.

"We're asking the court to declare that these five education codes are unconstitutional and that they violate the equal protection clause," Marcellus A. McRae, one of several attorneys arguing on behalf of plaintiffs, told Reuters.

Minority students are disproportionately affected because many live in poorer neighborhoods where teacher turnover and other problems are more prevalent, according to Students Matter, the group behind the lawsuit.

"I'm here today because my education is very important to me," lead plaintiff Elizabeth Vergara, 16, told a news conference during a break in the hearing. "Right now we're kids and we can't do this alone."

Students Matter boasts the firepower of a Los Angeles law firm that mounted a team of many of the same attorneys to successfully overturn California's anti-gay marriage initiative, Proposition 8.

HARMING DISADVANTAGED STUDENTS

Taken together, the laws harm poor and disadvantaged students on several levels, McRae said. First, a law regulating how layoffs of teachers must be performed requires districts to fire those with the least seniority first.

This can lead to higher turnover at schools in poorer areas because those are the schools where the younger teachers are often assigned first, he said.

The problem is exacerbated, McRae said, by another law, which grants teachers tenure, near lifetime employment, if they are viewed as successful after two years on the job.

Practically speaking, that law means it is so difficult to fire tenured teachers that the ineffective ones wind up getting transferred to schools in undesirable locations, McRae said.

Lawyers for the state and for teachers unions have argued there is no proof the regulations harm students.

"Tenure and freedom from arbitrary dismissal is crucial to recruit and retain quality teachers," James Finberg, representing the California Teachers Association and California Federation of Teachers, told the court.

"Teachers do their best when they have good working conditions including job security," he said.

Deputy Attorney General Nimrod Elias said earlier in the case "the occasional and random assignment of a student to a bad teacher" does not meet the test for an equal protection case.

"The statutes don't assign teachers. Districts and principals assign teachers," he said. "The reality of students being in inner-city schools is not caused by these statutes."

The state and teachers union further argued that the laws give school administrators adequate discretion to make employment decisions that as a whole have succeeded in attracting and retaining quality instructors.

Los Angeles Superior Court Judge Rolf Treu gave the two sides until April 10 to submit final written arguments in the case, and said he would rule within 90 days after that. (Additional reporting by Alex Dobuzinskis, Writing by Sharon Bernstein in Sacramento; Editing by Ken Wills and Toni Reinhold)